Researcher Lance Kriegsfeld sits in his office looking intently at two rats circling each other on his computer screen.
“Notice how she crosses his path. That’s called a run-by,” says Kriegsfeld, an assistant professor and behavioral neurobiologist in the psychology department. He says a touch-back is when the female rat teasingly approaches and retreats, and an interception is when another female diverts the male’s attention. “For some reason, they’re all football terms.”
Finally, the male mounts the female, freezes for a moment, and raises his little paws in the air. “That’s classic ejaculation,” Kriegsfeld says, chuckling.
Kriegsfeld studies how daily, or circadian, rhythms affect hormones in the brain. Hormones are the body’s communication chemicals, and Kriegsfeld, with colleagues such as George Bentley at the Helen Wills Neuroscience Institute, focuses on two reproductive brain hormones, GnIH and GnRH. Looking at these two chemicals, Kriegsfeld and colleagues have solved one of the biggest mysteries in fertility and found a key that may make it easier for certain working women to conceive.
The mystery surrounds the giant burst of hormones released just as mammals ovulate. Conventional wisdom says the burst is brought on when GnRH—an aphrodisiacal brain hormone that tells the gonads to produce testosterone and estrogen before ovulation and sex—seemingly shifts from neutral into drive.
Through their work with rodents, Kriegsfeld and colleagues found that another hormone enters the mix. A complementary chemical, GnIH—the brain equivalent of a cold shower—may be a long-sought-after missing link into how ovulation happens.
GnIH is an inhibitor that researchers, until five years ago, weren’t sure even existed. Like a yin to the GnRH yang, it could stop the rat on Kriegsfeld’s screen in his tracks as if, say, a cat were to walk by. It turns out that during most of the reproductive cycle, GnIH acts like a sentry guard, inhibiting the buildup of estrogen and other hormones. Kriegsfeld and colleagues found that just as the egg is ready to be released, the sentry takes a “coffee break,” allowing for the surge in hormones.
“We’re looking at two systems sort of flip-flopping their roles,” Kriegsfeld says.
The discovery may have far-reaching implications for fertility. Humans, like rats, ovulate on a regular circadian rhythm. Because of this, flight attendants and shift workers constantly changing sleep schedules have trouble getting pregnant and are plagued by miscarriages. Understanding the role of GnIH could help women struggling with fertility to improve their chances of conceiving and carrying to term.
From the November December 2006 Life After Bush issue of California.